1. Technical Field
The present invention relates to a substance detection method and a substance detection device.
2. Related Art
Recently, as a highly sensitive spectroscopic technique for detecting a sample molecule at a low concentration, an affinity sensor utilizing localized surface plasmon resonance (LSPR) or surface-enhanced Raman scattering (SERS) for qualitative and quantitative detection directly from vibrational spectroscopy has attracted attention. SERS is spectroscopy in which an enhanced electric field is formed on a metal surface with a nanometer-scale convex-concave structure, and Raman scattered light is enhanced by 102 times to 104 times, thereby enabling highly sensitive detection. A target molecule (target substance) is irradiated with linearly polarized excitation light with a single wavelength such as a laser, and scattered light (Raman scattered light) with a wavelength which is shifted from the wavelength of the excitation light by the molecular vibration energy of the target molecule is spectroscopically detected, whereby a fingerprint spectrum is obtained. Based on the shape of this fingerprint spectrum, the target substance can be identified.
It has been confirmed that there is a correlation between tracheal inflammation due to asthma and the concentration of NO (nitrogen monoxide) contained in the breath, and the concentration of NO in the breath has been recognized as an index of asthma. As a sensor chip for detecting such NO, a sensor chip focusing on surface plasmon resonance (SPR) which is a light sensing technique has been proposed. For example, APPLIED SPECTROSCOPY, Volume 65, Number 8, 825-837, 2011 (NPL 1) describes that a biological enzyme called “cytochrome P450” is disposed on an LSPR substrate (sensor chip) having an Ag microstructure, and NO is allowed to react with the cytochrome P450 enzyme, and the SERS signal of the reactant is obtained.
However, when a sensor chip having an organically modified film for trapping NO (target substance) as described above is irradiated with laser light, the organically modified film may sometimes be deteriorated by the laser light. Due to this, NO cannot be detected with high sensitivity in some cases.